Method for treating ammonia-containing organic waste

ABSTRACT

A method is described for treating animal manures and other organic wastes to destroy pathogens, reduce noxious odors, and immobilize water-soluble pollutants, thereby producing a pasteurized, granular product useful as a soil amendment. In a described implementation, the solids content of the organic waste is raised to a predetermined level to create air-filled pore space, and the pH is raised sufficiently to liberate endogenous gaseous ammonia in the air-filled pores for a predetermined time. The level of gaseous ammonia is sufficient to significantly destroy pathogens in the manure. In addition, alkaline material and/or iron salts are added to the organic waste to render certain water-soluble pollutants insoluble.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/071,205 filed May 1, 1998, now U.S. Pat. No. 6,248,148 theentire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of wastemanagement, and in particular to a method for treatingammonia-containing organic waste, including but not limited to animalmanures. Embodiments of the present invention can be applied to destroypathogens, reduce noxious odors, and immobilize water-soluble pollutantsin such organic waste, rendering the treated waste material safe forstorage and application to land as, for example, a fertilizer, limingagent or soil amendment.

Since ancient times, animal manures were recycled back to the land thatprovided the animal feed, thereby completing the nutrient cycle. Asanimal production became intensified, the cycle was broken, withchemical fertilizers increasingly used to produce animal feed and theanimal manure accumulating at the point of production as an unwantedwaste. In many parts of the U.S., Europe and other countries, manureproduction at large, confined animal feeding operations (CAFOs),primarily poultry, swine, dairy and beef, has resulted in odor, nutrientrunoff and pathogen food-chain contamination problems. Until thepresent, little attention has been placed on the processing of animalmanure to address these problems, with most attention being placed onso-called “best management practices” to contain the manure and ensurethat it is applied at agronomic rates. Because of the largeconcentrations of animal manures at CAFOs, generally well in excess oflocal needs, the need has arisen to treat manures so that they can beeasily stored without causing odor or nutrient leaching problems, togreatly reduce pathogen levels and protect against food-chaincontamination, and to create products that have a wide range of utilityas fertilizers and soil amendments.

A wide range of technologies were developed to treat wastewaterresiduals and sewage sludges for pathogen destruction and odor controlin response to the large public works expenditures for wastewatertreatment in the U.S. in the 1960s and 1970s. Prominent among these weretechnologies that used alkaline reagents to destroy pathogens, to reduceodors, and to solidify and granulate dewatered sewage sludges to makeproducts that could be used beneficially. The standards that thesetechnologies had to meet were the U.S. EPA regulations for pathogenreductions (see 40 C.F.R. §§257, 503) and vector attractions (40 C.F.R.§503).

A traditional approach to alkaline stabilization of sewage sludges hasbeen the use of lime (CaO) to raise pH to around 12 or to produce heatby exothermic hydrolysis. Alternative technological approaches haveinvolved the use of less expensive alkaline mineral by-products. Patentsexemplifying such approaches include U.S. Pat. No. 4,554,002 toNicholson; U.S. Pat. No. 4,781,842 to Nicholson; U.S. Pat. No. 4,902,431to Nicholson et al.; and U.S. Pat. No. 5,277,826 to Burns et al. Suchpatents teach the use of a range of alkaline materials to raise pH toaround 12 and to increase total solids as a means of destroyingpathogens.

In addition, the use of ammonia to kill pathogens in sewage sludge isdisclosed in U.S. Pat. No. 4,793,927 to Meehan et al. Meehan describesthe addition of ammonia-containing compounds to sewage sludge as anagent to destroy bacterial, parasitic and viral pathogens within thesludge matrix. U.S. Pat. No. 5,143,481 to Schumacher et al. shows howfluidized bed combustion residue (FBCR), or fly ash, containing CaO canbe used to treat sewage sludges by producing heat in an exothermicreaction. U.S. Pat. No. 5,679,262 to Girovich et al. describes the useof mineral by-products to reduce the use of CaO in order to killpathogens and achieve a dry product. Finally, U.S. Pat. No. 5,417,861 toBurnham teaches how a combination of surviving microflora, salt levelsand solids content can provide long-term stability to bioorganic orwastewater sludges.

Despite these extensive efforts directed at the treatment of wastewaterand sewage sludge, no comparable technologies have been developed forthe treatment of ammonia-containing organic waste such as animalmanures. Manure treatment, for example, has historically included onlyaerobic and anaerobic digestion of liquid manures, while some beef andpoultry manure is composed (see D. L. Day and T. L. Funk, ProcessingManure: Physical, Chemical, and Biological Treatment (1998) (publishedin J. L. Hatfield and B. A. Stewart, Animal Waste Utilization: EffectiveUse of Manure as a Soil Resource (Ann Arbor Press 1998)). The onlysignificant known approach to chemical stabilization of manure is theaddition of calcium, iron or aluminum salts to poultry manure to reduceammonia emissions and to immobilize soluble phosphorus (see P. A. Moore,Jr. et al. and D. M. Miller, Reducing Phosphorus Solubility in PoultryManure with Aluminum, Calcium and Iron Amendments, J. Environ. Qual.,vol. 23, 325-330 (1994)); and U.S. Pat. No. 3,877,920 to Carlberg, whichtaught the use of fly ash to deodorize animal manures. None of theseapproaches, however, deal with chemical treatment of animal manure forpathogen destruction.

With respect to pathogen destruction in animal manures, M. B. Jenkins etal., Inactivation of Cryptosporidium parvum Oocysts by Ammonia, Appl.and Env. Microbiol., Vol. 64, 784-788 (1998), shows that freeammonia-containing solutions can destroy Cryptosporidium parvum oocystsin liquid media and suggests that ammonia in manures might be used tokill oocycsts of this organism, but this reference only discusses theuse of free ammonia in solution. Large-scale introduction of aqueousammonia to animal manures presents a host of practical problems,including, but not limited to, problems associated with the handling oflarge quantities of a potentially-hazardous liquid. The introduction ofliquids to manure is counterproductive because manures are inherentlywet and need to be dewatered for effective handling and storage.Moreover, aqueous ammonia is caustic, relatively expensive and difficultto handle.

Another problem with respect to the treatment of manures, especiallywhere the treated material is to be used as a soil amendment, relates tothe high levels of water-soluble phosphorous and water-soluble traceelements that are often found in such waste material. For example, theapplication of manure to land in amounts optimal to satisfy nitrogenrequirements for crops can result in a buildup of water-solublephosphorous in the soil, since crop demands for phosphorous aregenerally much lower than those for nitrogen. This can lead toundesirable runoff of phosphorous during rainfall events andeutrophication of surface waters like lakes, streams and impoundments.Similarly, high levels of water-soluble trace elements, such as copperand zinc, can be phytotoxic to crops, particularly for acidic soils.

In view of the foregoing, it is apparent that there is a need for safe,effective and economical methods for disinfecting and deodorizing animalmanures and other organic wastes that takes advantage of the inherentendogenous ammonia in such waste materials. Moreover, in order to avoidenvironmental problems often associated with land application ofmanures, it is desirable that such methods limit the level ofwater-soluble phosphorous, copper and zinc in the end product.

SUMMARY OF THE INVENTION

The present invention is directed to methods for disinfecting anddeodorizing animal manures and other organic wastes containing ammonia,while also reducing the levels of water-soluble pollutants such asphosphorous, copper and zinc. In accordance with a particularembodiment, the solids content of a sample of animal manure is raised toan approximate minimum of 30% so as to create air-filled pore space. Inaddition, the pH of the animal manure is raised to an approximateminimum of 9.5 to liberate endogenous gaseous ammonia in the air-filledpores for at least 1 hour, the level of gaseous ammonia being sufficientto reduce E. coli levels to less than 3.3*10² colony forming units/gram(dry weight) and Salmonella levels to less than 6.7*10² colony formingunits/gram (dry weight), and to significantly reduce the levels ofviruses and parasites. Subsequent to, or in conjunction with, thispathogen destruction, alkaline material and/or iron salts are added tothe waste material to immobilize water-soluble pollutants. Such methodsproduce a granular, deodorized product suitable for use as a soilamendment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating the effect of pH on ammonia gasproduction.

FIG. 2 is a flow diagram illustrating a general method for treatingammonia-containing organic waste in accordance with an embodiment of thepresent invention.

FIG. 3 is a flow diagram illustrating a method for treatingammonia-containing organic waste in accordance with another embodimentof the present invention.

FIG. 4 is a graph illustrating the effect of fluidized bed coal ash onthe level of water-soluble phosphorous in cow manure followingdisinfection.

FIG. 5 is a graph illustrating the effect of ferrous chloride on thelevel of water-soluble phosphorous in cow manure following disinfection.

DETAILED DESCRIPTION

The present invention is directed to methods for treating animal manuresand other ammonia-containing organic wastes. In accordance withparticular embodiments described below, such organic waste isdisinfected and deodorized to produce a pasteurized, granular productsuitable for use as a soil amendment. In addition, water-solublepollutants in the organic waste are immobilized. Unlike knownapproaches, methods in accordance with the present invention takeadvantage of the superior effectiveness of gaseous ammonia in achievingpathogen kill as compared to aqueous ammonia.

Ammonia gas is a known chemical agent for achieving pathogen kill, asdescribed in U.S. Pat. No. 4,793,972, issued to Meehan et al. for aninvention involving the treatment of sewage sludge in which ammonia wasadded and the pH was raised to near 12. In addition, the role of ammoniaas a disinfectant for Cryptosporidium parvum has been recognized in, forexample, M. B. Jenkins et al., Inactivation of Cryptosporidium parvumOocysts by Ammonia, Appl. and Env. Microbiol., Vol. 64, 784-788 (1998),but such studies only considered free ammonia dissolved in water and didnot identify the superior role of gaseous ammonia compared to dissolvedammonia in pathogen kill. In a material that contains solids and water,such as animal manure, and at the normal pH levels of animal manure, anyammonia in the material or added to the material (including as taught byMeehan) would exist as a dissolved gas or as ammonium ion.

Ammonia gas has a high solubility in water, and except at high pH levelsexists as the ammonium ion. The equilibrium between dissolved ammonia(NH₃₍₁₎) and ammonium ion (NH₄ ⁺) is given by the equation:

NH₃₍₁₎+H⁺⁼NH₄ ⁺  (Eq. 1)

This equation shows that the amount of dissolved ammonia increases asthe pH increases (i.e., the concentration of H+ decreases). Toillustrate, FIG. 1 maps the percentage of ammonia as dissolved ammoniaas a function of pH, showing that free ammonia (NH₃) is produced when pHis greater than about 9.5 and reaches a maximum near pH 12.

In view of the relationship illustrated in FIG. 1, embodiments of thepresent invention are directed to treatment processes (1) in which pH israised to a level sufficient to release significant endogenous ammoniafrom the manure, yet low enough not to release so much ammonia as tocause an odor problem, (2) that minimize the loss of fertilizernitrogen, and (3) that do not significantly add to ammonia airemissions. Such treatment processes include increasing the solidscontent of the manure so as to increase the air-filled pore space and tocreate a reservoir in which gaseous ammonia can be liberated and cancontact and kill pathogens in the manure. Increasing the solids contentenhances the killing effect of the endogenous ammonia in the manure andreduces the need to raise pH to the very high levels (e.g., near 12)used in previously known waste treatment approaches. By so doing, theodor problems associated with large ammonia releases and the loss offertilizer nitrogen can be minimized.

FIG. 2 illustrates a general method for treating ammonia-containingorganic waste in accordance with an embodiment of the present invention.Once a collection of organic waste material is obtained (Step 10), themethod of this embodiment generally involves creating air-filled porespace within the organic waste material (Step 15). This can be done, forexample, by increasing the solids content of the organic waste to atleast approximately 30%. A portion of the endogenous ammonia is thenconverted to gaseous ammonia in the air-filled pore space (Step 20).This can be done, for example, by raising the pH of the organic wastematerial to a minimum of approximately 9.5.

To illustrate a specific implementation of an embodiment such as thatillustrated in FIG. 2, consider a case in which a 5-ton collection ofchicken manure (e.g., removed from a poultry house) is to be treated.Such chicken manure typically has a solids content of approximately 20%and a pH of approximately 6.8. Referring now to FIG. 3, once thecollection of chicken manure is obtained (Step 25), bulking material isadded to the semi-liquid collection of chicken manure using, forexample, a mixing device such as an auger-mixer or a front-end loader(Step 30). A wide variety of materials are suitable for use as a bulkingmaterial including, for example, fluidized boiler ash (a by-product ofindustrial air scrubbing processes). The bulking material is added in anamount sufficient to raise the solids content of the collection toapproximately 30% or above (Step 35). In this example, approximately1,400 pounds of fluidized boiler ash is generally sufficient. During themixing process, it is desirable to monitor the pH of the mixture (Step40). In some cases, it may be necessary to mix in additional alkalinematerials (e.g., lye, lime, or similar material) to achieve the desiredpH of approximately 9.5 or above, although the alkaline nature of thebulking material itself may be sufficient. The mixture of manure andbulking material is then placed in an enclosed area (e.g., a bunker), oreven simply covered with a tarp, for a period of approximately 1 hour ormore to entrain the evolved ammonia (Step 45). At the completion of thisincubation period, the mixture can be safely used for spreading onagricultural fields, mixed with other materials for soil blends, andmany other similar uses.

The level of gaseous ammonia produced by a method such as those shown inFIG. 2 and FIG. 3 will generally be sufficient to reduce E. coli levelsto less than 3.3*10² colony forming units/gram (dry weight) andSalmonella levels to less than 6.7*10² colony forming units/gram (dryweight), and to significantly reduce the levels of viruses andparasites. Moreover, the method produces a product that is granular anddeodorized for use as a soil amendment.

All animal manures contain significant quantities of ammonia. Table 1below summarizes the total ammonia-nitrogen (NH₃—N) contents ofdifferent types of animal manures. This data indicates that all animalmanures will typically contain enough total ammonia to provide gaseousammonia for disinfection, under the appropriate process parameters ofpH, solids and time of treatment, in accordance with embodiments of thepresent invention.

TABLE 1 Average Ammonia-Nitrogen in Animal Manures Ammonia-NitrogenAnimal Type (mg/kg)* Beef cattle 3500 Dairy cattle 2000 Poultry 130000 Swine 3000 Turkey 8500 Sheep 2500 Horses 2000 *Assumes no bedding.Source: Bull, Ohio Livestock Manure and Wastewater Management Guide 604(Ohio State University 1992).

Ammonia gas has a very high solubility in water (˜32% by weight). Thisis represented quantitatively by the Henry's Law Constant for ammonia of5.76×10⁴ mol m⁻³atm⁻¹. This value is 1700 times greater than that ofcarbon dioxide and almost 50 times greater than that of sulfur dioxide.Eq. 1 and FIG. 1 show that ammonia can be generated by raising pH aboveabout 9.5, but if the manure is too wet, there will be enough free waterto dissolve the ammonia and prevent free contact of ammonia gas withmanure pathogens. When a dry mineral material like fly ash, cement kilndust or lime kiln dust is mixed in sufficient quantities, or the manureis otherwise dried, free water in the manure is absorbed by the solidsor otherwise removed, and pore space is created in the mixture. If thesolids content of the mixture is high enough, there will be enoughair-filled pore space in the mixture for ammonia gas to be liberatedwithin the material when the pH is raised. Converting free ammonia fromthe dissolved to the gaseous form increases the effectiveness of theendogenous ammonia in the manure in killing pathogens. Fly ash additionincreases solids content, total porosity and air-filled porosity,thereby increasing the amount of gaseous ammonia in the manure. If analkaline material is used that generates heat through exothermichydrolysis with water in the manure, a lower solids content and pH maybe acceptable to achieve the same level of gaseous ammonia in theair-filled pore space.

The following examples illustrate the effectiveness of organic wastetreatment methods in accordance with embodiments of the presentinvention. In a first example, increasing the pH of sterile chickenmanure, seeded with E. coli and Salmonella, by the addition of NaOH, ledto an increased evolution of ammonia gas into the headspace and adecrease in the survival of the seeded bacteria. This bactericidaleffect was enhanced when the chicken manure contained less water (i.e.,more solids). Initial reaction mixtures of 20 grams of sterile chickenmanure, seeded with overnight cultures of E. coli and Salmonella, wereadjusted to 30% solids or 15% solids with the addition of either 5 MNaOH and water (pH 9.5 reactions) or sterile water alone (pH<8.5reactions). The reaction mixtures were mixed extensively and split into5 gram (30% solids) or 10 gram (15% solids) aliquots. The reaction tubeswere then placed in a 30° C. incubator, tested for pH by electrode orplaced in a 250 ml chamber for ammonia headspace analysis withammonia-specific pull tubes. Tubes were removed from the incubator after1 and 3 hours incubation and assayed for surviving E. coli (growth on E.coli Petrifilm (3M, Minneapolis, Minn.)) and Salmonella (black colonygrowth on XLD agar plates). The results are presented in Table 2.

TABLE 2 Effect of pH and % Solids on Survival of Seeded E. coli andSalmonella in Chicken Manure Headspace Bacterial CFU*/gram (dry weight)Ammonia Initial Inoculation 1 Hour Incubation 3 Hours IncubationReaction pH (ppm) E. coli Salmonella E. coli Salmonella E. coliSalmonella Chicken Manure - 7.9  430 3.1E+04 2.5E+04 1.2E+04 1.0E+05 1.1E+04 4.0E++05 15% solids Chicken Manure - 9.3 1540 ″ ″ 4.7E+031.0E+05 <3.3E+02 <6.7E+02 15% solids Chicken Manure - 8.3  180 ″ ″6.7E+03 1.0E+05  7.7E+03  6.7E+04 30% solids Chicken Manure - 9.3 1240 ″″ <3.3E+02  <6.7E+02  <3.3E+02 <6.7E+02 30% solids *Colony Forming Units

In a second example, increasing the pH of sterile swine manure, seededwith E. coli and Salmonella, by the addition of NaOH, led to anincreased evolution of ammonia into the headspace and a decrease in thesurvival of the seeded bacteria. This bactericidal effect was enhancedwhen the swine manure contained less water (i.e., more solids). Initialreaction mixtures of 23.5 grams of sterile swine manure, seeded withovernight cultures of E. coli and Salmonella, were adjusted to 30%solids or 15% solids with the addition of either 5 M NaOH and water (pH9.5 reactions) or sterile water alone (pH 8.8 reactions). The reactionmixtures were mixed extensively and split into 5 gram (30% solids) or 10gram (15% solids) aliquots. The reaction tubes were then placed in a 30°C. incubator, tested for pH by electrode or placed in a 250 ml chamberfor ammonia headspace analysis with ammonia-specific pull tubes. Tubeswere removed from the incubator after 1 and 3 hours incubation andassayed for surviving E. coli (growth on E. coli Petrifilm (3M,Minneapolis, Minn.) and Salmonella (black colony growth on XLD agarplates). The results are presented in Table 3.

TABLE 3 Effect of pH and % Survival on the Survival of seeded E. coliand Salmonella in Swine Manure Headspace Bacterial CFU*/gram (dryweight) Ammonia Initial Inoculation 1 Hour Incubation 3 Hours IncubationReaction pH (ppm) E. coli Salmonella E. coli Salmonella E. coliSalmonella Swine Manure - 8.8 130 3.1E+06 3.2E+06 1.0E+06 6.2E+05 1.3E+06 <1.0E+07 15% solids Swine Manure - 9.4 240 ″ ″ 2.3E+04 6.7E+02 4.3E+02 <6.7E+02 15% solids Swine Manure - 8.8 280 ″ ″ 9.9E+05 1.3E+06 5.5E+05 <1.0E+07 30% solids Swine Manure - 9.3 520 ″ ″ 8.7E+02<6.7E+02  <3.3E+02 <6.7E+02 30 solids *Colony Forming Units

These examples show that the three process variables used in accordancewith embodiments of the present invention—pH, solids and time—have asynergistic effect promoting the destruction of E. coli and Salmonellain animal manures to non-detectable levels. The total content of themanure does not change during processing, only the form of the ammoniaand the contact between gaseous ammonia and pathogens in the manure. Atthe lower pH, increasing the solids content had little effect ondestruction of E. coli and Salmonella after one hour. When pH was raisedto near 9.5, there was measurable pathogen destruction. However,substantially complete destruction of E. coli and Salmonella onlyoccurred when pH was raised to near 9.5 and solids content was raised to30%. In the case of the swine manure, because of the lower endogenousammonia than in chicken manure, a three hour process time was requiredto reduce E. coli to non-detectable levels. These results also show astrong association between gaseous endogenous ammonia and pathogendestruction. This process for pathogen destruction should be applicableto all ammonia-containing organic wastes.

In accordance with a variation on the above-described embodiments,levels of water-soluble pollutants, such as phosphorous and tracemetals, can be reduced by the addition of alkaline material byproducts(e.g., mineral byproducts) and/or iron salts subsequent to, or inconjunction with, pathogen destruction obtained by liberation of gaseousammonia from the organic waste. By combining pathogen destruction withphosphorous and trace element immobilization, such embodiments can beapplied to produce a soil amendment that avoids many of the limitationsof known approaches to handling animal manures and other organic wastesby helping to avoid transferring pathogens, phosphorous and traceelements to the food chain and water supplies.

For example, referring back to the embodiment illustrated in FIG. 2,immobilization of water-soluble pollutants can be achieved through theintroduction of a suitable quantity (see below) of an iron salt to theorganic waste material following the conversion of endogenous ammonia togaseous ammonia in Step 20. Iron salts that have been found to beeffective include ferrous chloride (FeCl₂), ferric chloride (FeCl₃),ferrous sulfate (FeSO₄) and ferric sulfate (Fe₂(SO₄)₃). With referenceto the embodiment illustrated in FIG. 3, the quantity of iron salt canbe mixed into the organic waste material following entrainment of theevolved ammonia in Step 45.

Alkaline materials, such as mineral byproducts, have also been foundeffective in immobilizing water-soluble pollutants. Such materials canbe introduced in suitable quantity (see below) in the same manner asjust described with respect to the use of iron salts. Materials usefulfor such applications include fluidized bed coal ash, fly ash, coalcombustion ash, flue gas desulferization byproduct, cement kiln dust,wood ash, pulverized limestone, rock fines, spent water treatment lime,and gypsum. It is also possible to reduce the quantity of iron saltsrequired to achieve a desired level of immobilization for certainpollutants by using a combination of alkaline materials and iron salts.

The following examples, the results of which are respectively presentedin FIG. 4 and FIG. 5, illustrate the effectiveness of organic wastetreatments methods in accordance with the above-described embodimentsfor immobilization of water-soluble pollutants. In each case, cow manurewas first reacted with NaOH to raise the pH to 10.5 for pathogenreduction. Following a two-hour reaction time, respective samples oftreated manure, having a solids content of approximately 30%, wasamended with fluidized bed coal ash (FBC) or ferrous chloride (FeCl₂) atdose rates of 20%, 30%, 40% and 50% by weight for FBC; and 0.5%, 1.0%,2.0% and 4.0% by weight for FeCl₂. The materials were reacted forperiods of up to 7 days, after which the treated manures were extractedwith water for one hour at a solid-to-water ration of 1:10 on a rotaryshaker. The levels of water-soluble phosphorous (P) were then determinedby standard methods (the results are presented as a percent reduction inwater-soluble P relative to the untreated manure, and were corrected fordilution by the additives).

As shown in FIG. 4, additions of 30-50% FBC initially reducedwater-soluble P by greater than 75%, which reductions declined over 7days to less than 50%. FIG. 5 shows that additions of 2-4% FeCl₂initially reduced water-soluble P by greater than 80%, which reductionswere maintained after 7 days.

Combinations of FBC and FeCl₂ are also effective in reducing levels ofwater-soluble P. For example, using a methodology identical to thatdescribed above with respect to FIGS. 4 and 5, samples of 20% and 30% byweight FBC and 2% and 4% by weight FeCl₂ were added alone and incombination, and the treated manure was tested at 2, 4 and 8 days. Asillustrated in Table 4 below, FBC alone reduced water-soluble P by 50%,regardless of the dose rate. FeCl₂ at 2% and 4% by weight reducedwater-soluble P by 80% and 99% respectively, and solubility did notchange between 2 and 8 days. Combining FBC and FeCl₂ enhanced the effectof the FeCl₂ at the 2% dose rate, but only slightly. FBC had no effectat the 4% FeCl₂ dose rate because the reduction in water-soluble P wasalready 99% with the FeCl₂ alone.

TABLE 4 Immobilization of Water-Soluble Phosphorous in Cow Manure withFBC, FeCl₂, and Combinations Thereof Treatment Day 2 Day 5 Day 7 20% FBC23 19 52 30% FBC 57 26 51  2% FeCl₂ 81 81 82  4% FeCl₂ 99 99 99 20% FBCand 2% FeCl₂ 89 89 87 20% FBC and 4% FeCl₂ 99 98 99 30% FBC and 2% FeCl₂96 90 93 30% FBC and 4% FeCl₂ 98 98 98

FBC, FeCl₂, and combinations of the two are also effective in reducingthe levels of water-soluble trace elements (e.g., copper (Cu), zinc(Zn)) from organic waste. Such reductions are especially advantageouswhen treating animal manures, since Cu and Zn are often added to animalfeed and can occur in high enough levels in animal manure to producecrop phytotoxicity when the manure is used as a soil amendment.

In one example, FBC and FeCl₂ were added to alkaline-treated cow manureand water extracts were made as previously described with respect to thereduction of water-soluble phosphorous levels. Cu and Zn levels in thewater extracts were determined by atomic absorption spectroscopy, usingstandard methods. FBC was amended at rates of 20% and 30% by weight,FeCl₂ was amended at a single rate of 2% by weight, and a combination of30% FBC and 2% FeCl₂ by weight was also evaluated.

As shown in Table 5 below, FeCl₂ at a dose rate of 2% by weightdecreased water-soluble Cu from 175-225 parts per billion (ppb) in theuntreated manure to 50-75 ppb. FBC, whether or alone or in combinationwith FeCl₂, had no appreciable effect in reducing levels ofwater-soluble Cu. On the other hand, both FBC and FeCl₂ decreased levelsof water-soluble Zn compared to the untreated manure. As with Cu, thecombination of FBC and FeCl₂ was not superior to FeCl₂ alone.

TABLE 5 Immobilization of Water-Soluble Copper and Zinc in Cow Manurewith FBC, FeCl₂, and Combinations Thereof Copper Zinc Treatment Day 2Day 8 Day 2 Day 8 microgram/liter Control 210 170 240  150  20% FBC 230150 140  50 30% FDC 340 170 70 50  2% FeCl₂  70  50 50 50 30% FBC + 2%FeCl₂  60  50 50 50

The variations discussed above for reducing levels of water-solublephosphorous and trace elements can be implemented, for example,generally in accordance with the basic embodiments illustrated in FIGS.2 and 3. For example, the process can be sequenced such that after thepathogen destruction step is substantially completed, a quantity ofFeCl₂ (or other iron salt) is added to immobilize P, Cu and Zn.

Persons skilled in the art of waste management will recognize that wastetreatment methods in accordance with embodiments of the presentinvention provide significant advantages over known processes that usehigher pH. Among these advantages are limiting ammonia release, therebylimiting hazards to workers from airborne ammonia, and keeping residualammonia with the end product, thereby maintaining the fertilizer valueof the end product. In addition, application of methods in accordancewith such embodiments makes it easier to reduce the pH of the endproduct after processing, thereby enhancing its utility in landapplications for soils that are already alkaline.

Although the present invention has been described principally withreference to embodiments for treating animal manures, persons skilled inthe art will recognize that it is equally applicable to other types ofammonia-containing animal wastes. For example, embodiments of thepresent invention may similarly be used to treat municipal wastewatersewage sludge, paunch manure, brewery sludge, and fermentation biomasswastes. Indeed, virtually any ammonia-containing organic waste materialis amenable to beneficial treatment in accordance with embodiments ofthe present invention.

The foregoing is a detailed description of particular embodiments of thepresent invention. The invention embraces all alternatives,modifications and variations that fall within the letter and spirit ofthe claims, as well as all equivalents of the claimed subject matter.For example, manures with high initial solids content (e.g., poultry orbeef cattle manure) may be treated by adding enough lime or caustic sodato raise the pH, while fly ash may be added to wetter manure (e.g.,swine manure) to achieve the required solids content and pH. Likewise, amixture of non-alkaline fly ash or other dry materials can be added toraise the solids content, and lime or caustic soda added to raise thepH. Mixing of the manure with the alkaline reagents may be accomplishedwith a variety of mixers (e.g., cement mixers, sewage sludge alkalinestabilization mixers, topsoil blenders), and the mixture may be held ina variety of enclosed vessels (e.g., plastic-covered windrows, silos,bunkers), depending on the scale of a particular operation. Personsskilled in the art will recognize from the foregoing detaileddescription that many other alternatives, modifications and variationsare possible.

What is claimed is:
 1. A method for treating organic waste material,said method comprising: reducing a level of pathogens within an organicwaste material by converting endogenous ammonia to gaseous ammonia andretaining the gaseous ammonia within the organic waste material; andimmobilizing a pollutant within the organic waste material.
 2. Themethod of claim 1, wherein said immobilization comprises adding aquantity of an iron salt to the organic waste material.
 3. The method ofclaim 2, wherein the iron salt is selected from a group includingferrous chloride, ferric chloride, ferrous sulfate, and ferric sulfate.4. The method of claim 2, wherein the quantity of iron salt addedcomprises at least approximately 1% by weight of the organic wastematerial being treated.
 5. The method of claim 1, wherein saidimmobilization comprises adding a quantity of an alkaline material tothe organic waste material.
 6. The method of claim 5, wherein thealkaline material is selected from a group including fluidized bed coalash, fly ash, coal combustion ash, flue gas desulferization byproduct,cement kiln dust, wood ash, pulverized limestone, rock fines, spentwater treatment lime, and gypsum.
 7. The method of claim 1, wherein saidimmobilization comprises adding iron salt and alkaline material to theorganic waste material.
 8. The method of claim 1, wherein the pollutantis selected from a group including water-soluble phosphorous andwater-soluble trace metals.
 9. The method of claim 8, wherein thewater-soluble trace metals include copper and zinc.
 10. The method ofclaim 1, wherein said pathogen reduction comprises adding a quantity ofa mineral byproduct to the organic waste material, wherein the mineralbyproduct chemically reacts with the organic waste material to liberateendogenous ammonia and to render a water-soluble pollutant within theorganic waste material insoluble.
 11. The method of claim 10, furthercomprising adding iron salt to the organic waste material after thelevel of pathogens has been reduced.
 12. The method of claim 11, whereina pH level of the organic waste material is maintained aboveapproximately 8.5 for a period of at least approximately 24 hoursfollowing addition of the iron salt.
 13. The method of claim 1, whereinthe organic waste material comprises a material selected from a groupincluding municipal wastewater sewage sludge, paunch manure, brewerysludge, and fermentation biomass wastes.
 14. The method of claim 1,wherein the organic waste material comprises animal manure.
 15. Themethod of claim 14, wherein the organic waste material further comprisesmanure from an animal selected from a group including beef cattle, dairycattle, poultry, swine, turkeys, sheep, and horses.
 16. The method ofclaim 14, wherein the organic waste material further comprises beddingmaterial.